1. Field of the Invention
The invention is directed to an improved fuel injection system for an internal combustion engine.
2. Description of the Prior Art
One fuel injection system of the type with which this invention is concerned, known from German Patent Disclosure DE 39 00 763 A1 has a high-pressure fuel pump and a fuel injection valve for each cylinder of the engine. The high-pressure fuel pump has an engine-driven pump piston defining a pump work chamber, and a communication of the pump work chamber with a relief chamber is controlled by an electrically controlled valve. The fuel injection valve has an injection valve member, by which at least one injection opening is controlled, and which is movable in an opening direction, counter to the force of a closing spring, by the pressure prevailing in a pressure chamber that communicates with the pump work chamber. The closing spring is braced on one end at least indirectly on the injection valve member and on the other at least indirectly on a storage piston. The storage piston, on its side remote from the closing spring, is subjected to the pressure in the pump work chamber and is movable in a stroke motion counter to the force of the closing spring. The storage piston is movable from an outset position, at low pressure in the pressure chamber, into the storage chamber, and the deflection stroke motion of the storage piston into the storage chamber is limited by a stop. The storage piston has a shaft part, guided in a connecting bore between the storage chamber and the pump work chamber, and outside the connecting bore in the storage chamber, it has a larger cross section than on the shaft part. By means of a throttling gap located between the connecting bore and the shaft part, damping of the deflection stroke motion of the pump piston is accomplished, since here fuel positively displaced from the pump work chamber into the storage chamber has the pass through the throttling gap, which causes damping of the motion of the storage piston. The damping of the motion of the storage piston can either be constant over the stroke of the storage piston or such that the damping is strong at the onset of the deflection stroke motion and then decreases. It has been found that the damping attained in this way is insufficient, and thus the storage piston strikes the stop at high speed, causing irritating noises.